Learning Bone Growth 4: The Osteocyte

Learning Bone Growth 4 – The Osteocyte - focuses on the cell that is the star of the show in a network so complex that it rivals the human brain, and is analogous in many ways: there are  42 billion cells, versus 86 billion in the brain, 6 times the population of the earth, packed in in a small volume, 1.75 liters  versus 1.2 for the brain. The number of connections is astonishing, some 23 trillion. The osteocyte lives decades and is the ultimate multi-tasker. It is the one cell in ten that survives the 10-day process of surrounding itself with unmineralized osteoid, and is imbued with a lifetime that may be limited by the remodeling process but can last many decades. The osteocyte buried in bone in its lacuna extends multiple dendrites, filamentous cellular processes, each part of a complex network for “hand-to-hand” communication with neighbors, surface cells, vessels, and even the marrow. As it creates its specialized environment, each osteocyte creates an array of canaliculi around its, each a tunnel containing a single dendrite. Osteocytes represent 95% of the body’s bone cells, each developing from a mesenchymal stem cell (MSC) through osteoblast differentiation, responsible for multiple tasks. The mature osteocyte is a: mechano-sensor that coordinates mechanical adaptive responses; regulator of bone remodeling through control of osteoblasts and osteoclasts; endocrine cell sending hormones to other body systems and signaling markers locally; and regulator of calcium, phosphate and acid base metabolism. In so far as we are aware, this video demonstrates the stages in the formation of osteoctyes in human material for the first time.